1. Field of the Invention
This invention relates to a process for inhibiting or preventing fouling in refinery and petrochemical feedstocks during processing. More particularly, this invention relates to inhibiting distillate fuel fouling, manifested by particulate formation and gum generation in distillate fuel oils.
2. Description of the Prior Art
During hydrocarbon processing, transportation and storage, the hydrocarbons deteriorate, particularly when subjected to elevated temperatures. The deterioration usually results in the formation of sediment, sludge or gum and can manifest itself visibly by color deterioration. Sediment, sludge or gum formation may cause clogging of equipment or fouling of processing equipment (such as heat exchangers, compressors, furnaces, reactors and distillation systems, as examples). The fouling can be caused by the gradual accumulation of high molecular weight polymeric material on the inside surfaces of the equipment. As fouling continues, the efficiency of the operation associated with hydrocarbon processing equipment such as heat exchangers, compressors, furnaces, reactors and distillation systems decreases. The distillate streams which can result in significant fouling include the straight-run distillates (kerosene, diesel, jet), naphthas, lube oils, catalytic cracker feedstocks (gas oils), light and heavy cycle oils, coker naphthas, resids and petrochemical plant feedstocks.
The precursors leading to the formation of the foulants may form in tankage prior to hydrocarbon processing. Unstable components may include such species as oxidized hydrocarbons (for example, aldehydes and ketones), various organosulfur compounds, olefinic hydrocarbons, various inorganic salts and corrosion products.
Suggestions of the prior art for inhibiting the fouling rate in process heat transfer equipment include U.S. Pat. No. 3,647,677, Wolff et al., which discloses the use of a coke retarder selected from the group consisting of elemental phosphorous and compounds thereof to retard the formation of coke in high-temperature petroleum treatments.
Also, U.S. Pat. No. 4,024,048, Shell et al., teaches that certain phosphate and phosphite mono and diesters and thioesters in small amounts function as antifoulant additives in overhead vacuum distilled gas oils employed as feedstocks in hydrosulfurizing wherein such feedstocks are subjected to elevated temperatures of from about 200.degree. to 700.degree. F. U.S. Pat. No. 4,024,049, Shell et al., teaches that certain thio -phosphate and -phosphite mono-and di-esters in small amounts function as antifoulant additives in crude oil systems employed as feedstocks in petroleum refining which are subjected to elevated temperatures of from about 100.degree. to 1500.degree. F. Furthermore, U.S. Pat. No. 4,024,050, Shell et al., teaches that certain phosphate and phosphite mono- and di- esters in small amounts function as antifoulant additives in crude oil systems employed as feedstocks in petroleum refining which are subjected to elevated temperatures of from about 100.degree. to 1500.degree. F. U.S. Pat. No. 4,024,051, Shell et al., teaches the use of certain phosphorous acids or their amine salts as antifoulants in petroleum refining processes. U.S. Pat. No. 4,226,700, Broom, discloses a method for inhibiting the formation of foulants on petrochemical equipment which involves adding to the petrochemical, during processing, a composition comprising a thiodipropionate and either a certain dialkyl acid phosphate ester or a certain dialkyl acid phosphite ester. Moreover, U.S. Pat. No. 4,425,223, Miller, discloses that hydrocarbon process equipment is protected against fouling during processing of high sulfur containing hydrocarbon feed stocks by incorporating into the hydrocarbon being processed small amounts of a composition comprised of a certain alkyl ester of a phosphorous acid and a hydrocarbon, surfactant type, sulfonic acid.
U.S. Pat. No. 4,440,625, Go et al., teaches that hydrocarbon process equipment is protected against fouling by incorporating into the hydrocarbon being processed small amounts of a composition comprised of a dialkylhydroxylamine and an organic surfactant. Moreover, U.K. Pat. No. 2,157,670, Nemes et al., discloses a composition containing a hydroxylamine compound; a quinone, a dihydroxylbenzene, or an aminohydroxybenzene compound; and a neutralizing amine which is useful as an oxygen scavenger and corrosion inhibitor in boiler water and other aqueous systems. Additionally, U.S. Pat. No. 4,456,526, Miller et al, teaches that hydrocarbon process equipment is protected against fouling by incorporating into the hydrocarbon being processed small amounts of composition comprised of a dialkylhydroxylamine and a tertiary alkyl-catechol. U.S. Pat. No. 4,509,952, relates to an alkyldimethylamine ranging from C.sub.4 -C.sub.20 alkyl which may be added to a distillate fuel as a stabilizer to prevent fuel oil degradation.
However, none of these prior art references disclose the unique and effective mixture of a phosphite compound and a hydroxylamine compound in accordance with the instant invention for inhibiting the degradation, particulate and gum formation of distillate fuel oils prior to and/or during processing. SUMMARY OF THE INVENTION
This invention relates to processes for inhibiting the degradation, particulate and gum formation of distillate fuel oils prior to or during processing which comprises adding to the distillate fuel oil an effective inhibiting amount of a mixture of (a) a phosphite compound having the formula ##STR3## wherein R, R' and R" are the same or different and are alkyl, aryl, alkaryl or aralkyl groups, and (b) an effective amount of hydroxylamine having the formula ##STR4## where R.sup.III and R.sup.IV are the same or different and are hydrogen, alkyl, alkaryl or arlkyl groups, wherein the weight ratio of (a):(b) is from about 1:10 to about 10:1. More particularly, the processes of this invention relate to inhibiting the degradation, particulate and gum formation of distillate fuel oils prior to or during processing at elevated temperatures. Generally, the total amount of the mixture of (a) and (b) is from about 1.0 parts to about 10,000 parts per million parts of the fuel oil. It is preferred that the weight ratio of (a):(b) is from about 1:10 to about 10:1. This mixture of (a) and (b) provides an unexpectedly higher degree of inhibition of distillate fuel oil degradation than the individual ingredients comprising the mixture. It is therefore possible to produce a more effective inhibiting process than is obtainable by the use of each ingredient alone. Because of the enhanced inhibiting activity of the mixture, the concentrations of each of the ingredients may be lowered and the total amount of (a) and (b) required for an effective inhibiting and antifoulant treatment may be reduced.
Accordingly, it is an object of the present invention to provide processes for inhibiting the degradation, particulate and gum formation of distillate fuel oils prior to or during processing. It is a further object of this invention to inhibit fouling in refinery and petrochemical feedstocks (distillate fuel oils) during processing. These and other objects and advantages of the present invention will be apparent to those skilled in the art upon reference to the following description of the preferred embodiments.